XML 119 R102.htm IDEA: XBRL DOCUMENT v3.22.0.1

Off Balance Sheet Activities - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Allowance for credit losses relates to unfunded loan commitments	$ 1,000	$ 641

X

- Definition

Allowance for credit losses relates to unfunded loan commitments.

+ References

No definition available.

+ Details

Name:	fmao_AllowanceForCreditLossesRelatesToUnfundedLoanCommitments
Namespace Prefix:	fmao_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration